I use GSX for several years on FSX and P3D and never came across problems of installation. However I found the process to install the GSX Pro for MSFS a little too frustrating. Firstly I encountered the same problem that many simmers experienced, namely that " the Couatl engine has not started" I download the AddOn.EXE file as suggested but had to run it several times with and without Admin privilege to get some success . The program could just not delete some files and got hanged on some others. I also downloaded and replaced the file "bglmanx_fsdt.dat". I also did another updat via the Universal Updater. I still get errors and missing files as described here after,
Addon LFSB not installed or missing one or more files, skipping.
Traceback (most recent call last):
File "<string>", line 97, in loadAddons
File "<string>", line 49, in importAndCreateInstance
ImportError: No module named LFSB
About 10 lines further down I get this error
GSX SimStart
Error: exception UNRECOGNIZED_ID in call SetDataOnSimObject param #2 '-1359691040'
Error: exception UNRECOGNIZED_ID in call SetDataOnSimObject param #2 '-1359687792'
On the positive side, despite those errors , I was able to get the program running on MSFS after about 18 hours of fiddling with it.